The present invention relates to an apparatus for securing waste fragments machined from a workpiece on a spark erosion machine.
One such apparatus is generally known from German patent No. 27 55 724. A collecting plate for the waste fragments is formed by part of the workpiece supporting table, which is movable in one direction (e.g., the Y-direction) together with the workpiece and is consequently displaced relative to the wire electrode. Therefore, the supporting table must have an elongated slot in the Y-direction, whose length corresponds to the complete movement path between the electrode and the workpiece. However, in the other movement direction (X-direction) the supporting table is not movable, so that during a cutting movement in this direction the workpiece moves relative to the table. In other words, the supporting table remains stationary with respect to the electrode during a cutting advance in the X-direction. Thus, in this apparatus two additional sliding bearings are required for the supporting table or collecting plate, namely one sliding bearing permitting a displacement of the supporting table with respect to the bottom of the machine in the Y-direction and a second sliding bearing permitting a relative displacement of the table with respect to the cross-coordinate support in the X-direction. This is very complicated and costly. In addition, as a result of the slot formed in the supporting table in the Y-direction, the supporting table must be larger than the movement path, so that adequate stability is ensured. Thus, either the possible movement path is restricted or the machine is made more cumbersome and bulky. Finally, with this construction, it is only possible to remove the waste fragments from above the workpiece.
In general, when automatically cutting openings from a workpiece by means of spark erosion (e.g., in successively cut dies), the cut out "waste material" must be secured and removed.
For this purpose, apart from the aforementioned German patent No. 27 55 724, the following systems are known. Another possibility consists of the workpiece material being completely eroded away in the opening, so that there is no waste material to remove. However, this requires a longer eroding time, consumes unnecessary energy, and leads to an unnecessarily large consumption of electrode wire.
In another method, on cutting or eroding openings, the waste fragment is secured by holding webs connected to the workpiece, i.e. the opening is not completely cut. During a subsequent working process the holding web is broken away. However, this requires a further working process and also normally requires a reworking of the burr left behind after breaking away the holding web.